1. Field of the Invention
The present invention relates to a transistor component, particularly to a technique for obtaining a transistor component using a silicon grain. The present invention especially relates to a transistor component preferable for manufacture of large-size liquid crystal displays and the like.
2. Description of the Related Art
FIG. 11 is a planar view of an active matrix substrate in a conventional TFT (thin film transistor) liquid crystal display. A TFT is formed on each pixel area defined by data lines 31 and scan lines 15 on an insulating substrate 10.
As shown in FIG. 12(D), this TFT comprises a channel area 17 for forming a channel between a source area 14 and a drain area 16, a gate electrode 15 arranged opposite to the channel area 17 thereby sandwiching a gate insulation film 13, a source electrode 31 electrically connecting with the source area 14 via a contact hole 201 of a layer insulation film 20 formed on the surfaces of the channel area 17 and the source electrode 31, and a pixel electrode 40 made of a sputter ITO (indium thin oxide) film electrically connecting with the drain area 16 via a contact hole 202 of the layer insulation film 20. The source electrode 31 is here a portion of the data line, and the gate electrode 15 is a portion of the scan electrode. The same reference numerals have been indicated accordingly.
Conventionally, a TFT with the construction above was manufactured by the processes illustrated in FIG. 12. FIG. 12 is a cross-section of the conventional substrate in FIG. 11 taken along Xxe2x80x94X. As shown in FIG. 12(A), a semiconductor film is formed on the surface of a base protection film 11 of an insulating substrate 10, the semiconductor film is then patterned, formed to an island-shape, and a gate insulation film 13 is formed thereon.
Next, a thin film of aluminum or the like is formed by sputtering and patterned to form a gate electrode 15. Scan lines are formed concurrently. The gate electrode 15 is used as the mask for introducing an impurity ion on the semiconductor film, to form a source area 14 and a drain area 16. Thereafter, the layer insulation film 20 is formed. As shown in FIG. 12(B), contact holes 201, 202 are formed, and a source electrode 31 electrically connecting with the source area 14 via the contact hole 201 is formed. As shown in FIG. 12(C), an ITO film is formed by sputtering on the surface of the source electrode 31, and then a resist mask 701 is used as a mask to pattern the ITO film to form a mask. Then, as shown in FIG. 12(D), the resist mask 701 is used as a mask to pattern the ITO film and form a pixel electrode 40.
As described above, during the manufacture of an active matrix substrate for a TFT liquid crystal display, the CVD (chemical vapor deposition) or PVD (physical vapor deposition) method was used to form a semiconductor film on the substrate. Therefore, when manufacturing a TFT display having a silicon substrate of an area of 1 m2 or more, there was the problem that the device became bulky and the manufacturing cost increased.
As an alternative, compact silicon substrates could be combined to manufacture a TFT display with a large area, but the alignment would become complex, and the manufacture difficult.
On the other hand, recent efforts have been made to coat silicon solution on an insulating substrate and form a silicon film by removing the liquid, but even with this method, it is difficult to form a large-size silicon substrate. Accordingly, the conventional technique of forming transistor components and the like on a silicon substrate was not adequate in cases where large-size silicon substrates were required.
Another recent method liquidizes conductive material used for forming wiring, coating such liquid via an inkjet printer on the face for forming the wiring pattern, and blowing the solvent to form the wiring pattern. However, this problem had the issue that the step of forming the wiring pattern would be additionally necessary, etc.
In contrast to conventional semiconductor components formed on a silicon substrate, the present invention aims at providing a transistor component functioning as a semiconductor component by being quasi placed on an insulating substrate, and the method of manufacturing such transistor component.
The present invention further aims at providing an active matrix substrate for use with a large-size TFT liquid crystal display using the transistor component above, and a method of manufacturing such substrate.
The present invention still further aims at providing a semiconductor device enabling easy patterning of the wiring.
In order to solve the aims above, the semiconductor component relating to the present invention is formed by fixing a plurality of silicon microbulks (powder, grain or piece, etc.) on an insulating substrate in array, and using the silicon grains themselves as a channel layer of the transistor.
The present invention further uses the semiconductor component as the switching component for each pixel electrode of an active matrix substrate.
Furthermore, in the present invention, fine metal wires used for wire bonding in a conventional semiconductor device are used for the wiring pattern on the semiconductor component.
Also, the present invention is a semiconductor device having a contact hole in connection with a source area and a drain area of a semiconductor component, the contact hole being formed on an insulation film and formed of a cutout made by the insulation film being selectively cut by a fine cutting means.
The embodiment of the present invention described above comprises a silicon grain with a drain area and a source area formed via the channel area, an oxidation film covering the surface of the silicon grain, a gate electrode formed above the channel area via an oxidation film, a drain electrode electrically connecting with the drain area, and a source electrode electrically connecting with the source area.
The above structure allows the transistor component according to the present invention to be fixed on an insulating substrate made of plastic and the like, and use such transistor component with the desired functions. Accordingly, the difficulty of manufacturing large-size silicon substrates can be resolved. Furthermore, as there is no need to implement the step of forming the silicon film in the gaseous conditions of a vacuum apparatus, a substrate with low thermal resistance as described above can be used for the substrate.
In a preferred embodiment of the transistor component according to the present invention, the silicon grain is preferably substantially spherical and made of a silicon monocrystal. The oxidation film is preferably a silicon dioxide film. By using a substantially spherical silicon grain, it is easy to arrange the direction of the silicon grain when placing, arranging or fixing the transistor component according to the present invention on an insulating substrate. Also, by forming the silicon grain from a silicon monocrystal, the performance of the transistor component according to the present invention is enhanced. Forming the oxidation film covering the silicon grain out of silicon dioxide enables this silicon dioxide film to function as a gate electrode. The gate electrode may be formed as a ring surrounding the silicon grain.
The active matrix substrate for a liquid crystal display according to the present invention is structured so a transistor component is provided for each of a plurality of pixel areas defined by data lines and scan lines on an insulating substrate, the transistor component comprising a source area electrically connecting with the data lines, a gate electrode electrically connecting with the scan lines, and a drain electrode electrically connecting with a pixel electrode, wherein the transistor component is a transistor component according to the present invention. By using the transistor component according to the present invention as the switching component of the active matrix substrate for a liquid crystal display, it is possible to manufacture a large-size liquid crystal display.
In a preferred mode of working the active matrix substrate for a liquid crystal display according to the present invention, the transistor component is preferably fixed to the insulating substrate via an adhesive agent, and the adhesive agent is preferably coated on the insulating substrate corresponding to positions where the transistor component is to be arranged. Although the adhesive agent functions to fix the transistor component on the insulating substrate, the transistor component may also be fixed on the insulation film as SOG (spin on glass) and the like. The insulating substrate is preferably a plastic or flexible substrate, and the thermal resistance is preferably 200xc2x0 C. or less. According to the present invention, there is no need to adopt the CVD or other methods for forming a thin silicon film in a thermal environment of 300xc2x0 C. to 400xc2x0 C., so the active matrix substrate for use with a liquid crystal display can be manufactured in a low temperature environment.
A method of manufacturing a transistor component according to the present invention comprises the steps of forming a silicon grain from a silicon piece, forming an oxidation film on the silicon grain surface, forming a gate electrode above the area where the channel area of the silicon grain is to be formed, using the gate electrode as a mask to implant an impurity ion in the silicon grain, thereby forming a drain area and a source area, forming a drain electrode electrically connecting with the drain area, and forming a source electrode electrically connecting with the source area. According to this manufacturing method, the transistor component need only be placed at the desired location, so the step of separating the component required for conventional methods of manufacturing semiconductor components on a silicon substrate can be omitted.
One embodiment of the method for manufacturing the transistor component according to the present invention is preferably implemented under atmospheric pressure without using a vacuum device. The step of forming the silicon grain is preferably a step of forming a substantially spherical silicon grain, the silicon grain is preferably a silicon monocrystal, and the oxidation film is preferably silicon dioxide.
According to another method of manufacturing an active matrix substrate for a liquid crystal display according to the present invention, the substrate is provided with transistor components for each of a plurality of pixel areas defined by data lines and scan lines on an insulating plate, the transistor component comprising a source area electrically connecting with the data line, a gate electrode electrically connecting with the scan line, and a drain electrode electrically connecting with a pixel electrode, and wherein the transistor component is formed by the method of manufacturing the transistor component according to the present invention as described above.
As the preferred mode of the method of manufacturing an active matrix substrate for a liquid crystal display according to the present invention, the transistor component is preferably placed on the insulating substrate by using a dispenser, and the transistor component is preferably fixed on the insulating substrate via an adhesive agent. Especially, the adhesive agent is formed on the insulating substrate by using an inkjet-type recording head.
By employing this structure, there is no need to implement patterning by a photolithography step for the silicon film as conventionally required, thereby simplifying the manufacture steps. In this case, the adhesive agent may be formed on the insulating substrate at positions where the transistor components are to be formed by using an inkjet-type recording head.
Another embodiment of the present invention uses the fine metal wires themselves as the gate lines and/or source lines of the semiconductor component. Used are fine metal wires already in use in the field of IC mounting such as conventional wire bonding. By using the wiring technique of fine metal wires used in the field of IC mounting, it is possible to obtain a semiconductor device relating to the present invention as described herein.
Preferably from the aspect of low resistance, these fine metal wires are made of gold, aluminum, copper or an alloy of the foregoing metals, and have a width of some ten to hundred xcexcm. A semiconductor device using this wiring is used for an LCD or EL display. In order to prevent short-circuiting when the fine metal wires overlap with each other or with another conductive area, it is preferable to coat the surface of the fine metal wires with an insulation film. By using this insulation film as a layer insulation film or a gate insulation film, it is possible to omit the step of forming this insulation film.
Here, the fine metal wires themselves can be used as the source lines or gate lines of the semiconductor device. If there are any portions of the semiconductor where it is necessary to contact other areas, the insulating coating may be removed at such portions by selective etching. As result, the substrate to which this semiconductor device is applied may be a plastic, flexible or other substrate with a thermal resistance of 200xc2x0 C. or less.
As described above, prior art exists trying to form the metal wiring out of a liquid containing the wiring material, but by using the fine metal wires as the wiring pattern, it is possible to overcome the difficulties arising in this step.
Furthermore, the fine cutting means described above may be a dicing cutter. This cutter can form very fine cutouts, thereby enabling contact holes to be formed in also very fine silicon bulks.